Frequency domain identification of the complex Young's modulus of a viscoelastic solid from wave propagation experiment data is considered in this paper. The conventional techniques use a non-parametric approach, where the estimate at a particular frequency is independent of the estimate at another frequency. Here we show that the estimation accuracy can be improved significantly by taking the continuity of the complex modulus into account. In particular, we propose Bayesian estimation approaches to impose the continuity property. The estimation algorithms are computationally efficient. The analytical claims are also substantiated in experimental studies. (c) 2007 Elsevier Ltd. All rights reserved.